A fire service spokesman said the fire started at about 11.24am in the roof of the building on Colney Lane, but three crews from Carrow, Earlham and Sprowston found it was out by the time they arrived.

However, they used ladders and cut away roofing material so they could use a thermal image camera to see if the fire had spread.

They were stood down at 12.41pm, and the evacuation of the building has been lifted.

A spokesman for the institute said: “The incident was caused by smoke ingression from workers working on the roof. The smoke got into the building and moved along the roof space and entered the building.”

It is not believed anyone was injured, and neither police nor the ambulance service were called.